When my washing machine drains it sometimes comes up and out of the open pvc pipe in the service closet where the water heater would drain. I've found lots of posts where people speak of the washer standpipe overflowing, but can't find any info on what would cause my problem. When the washer drains I have to stand at the service closet (next to each other in the garage) and watch/listen. First I can hear gurgling, then hear the water coming up the pipe (similar to the sound of filling a glass of water), then I can see the water just before it emerges and floods my service closet and garage. If I turn the washer off and on as it drains this doesn't happen...but not really feasible for the long run. Any ideas?
It sounds like the pipe is partially blocked and water can only get through at a slower speed. The drain at the hot water is the lowest point so that's why it is coming from there. The blockage could be anything, from debris that came in through the pipe in the service closet or a sock that made it out of the washer. Since it's after where the water is coming out of the service closet then you might be able to get a drain snake the problem but you might have to get an expert to get it cleaned out.
lqlarry is likely right, and using a snake to clean out the line is the first step. (+1 Larry)
It could also be a problem with the plumbing vent. If that is the issue, you would likely hear a gurgle after you shutoff the washing machine and the water gets down to the P-trap, not unlike the sound the toilet makes at the end of the flush.
The other issue I can think of is that the plumbing drain is improperly sized or sloped. If that's the case, this problem would have always happened, and wouldn't be a new issue.
It's because the water flows out faster than the pipe can drain. The easiest way to fix this is to seal up the washing machine waste hose against the open PVC pipe. Some gaffer tape should do the trick.
Otherwise you could fit a holding tank above the drain which is allowed to fill and provides time enough for it to drain out without overflowing.
A harder option would be to increase the size of the waste pipe so that it can take a larger volume of water through it.
I only had that problem when I purchased a newer washer. I purchased a rubber piece from a hardware store, it came with two clamps that goes around each end. One end goes over the pipe and the other end goes over the rubber pipe to the washer. Tighten the clamps. No more problems with water backing out because of the tight seal. It didn't cost a lot and I didn't have to call a plumber which would have cost money and the problem not fixed.
I had the same problem with a new washer overflowing an old drain pipe. Tried snaking it, Drano-ing it, and plundgering it but no luck - it still would not drain fast enough to keep up with the washer. This pipe was very old and runs under the house, so way too much work to try and increase its flow rate any more invasive other way.
So I ended up reducing the flow rate of the drain hose from the washer by inserting a section of vinyl hose into it. Costs about $5 at the hardware store. I iteratively added flow-reducing notches to the hose until the rate was right.